This invention is generally directed to imaging members, and more specifically, the present invention is directed to single and multi-layered photoconductive imaging members comprised of novel crosslinkable polymers, and which polymers may, for example, be selected for the charge transport layer of the imaging members. More specifically, the present invention relates to crosslinkable hydroxylated polycarbonates, processes thereof, and charge transporting layers thereof. In embodiments thereof, the present invention relates to hydroxyl pendant polycarbonates crosslinked with a functionalized charge transport compound and a curing agent, and charge transport compositions comprised of charge transport compounds/molecules, and a hydroxyl pendant polycarbonate crosslinked with a functionalized charge transport compound and a curing agent. Also, in embodiments the crosslinked charge transport components of a hydroxyl-pendant polycarbonate crosslinked with a functionalized, such as hydroxy, known charge transport, especially hole transport, and a known curing agent can be selected for the charge transport layer of a photoconductive imaging member as the top overcoat protective layer for a photoconductive imaging member, or as a component in the charge transport layer of a photoconductive imaging member. The crosslinked charge transport compositions can be prepared as illustrated herein, such as by reacting a hydroxylated charge transport compound with a curing agent, such as a diisocyanate, in the presence of a solvent to form an isocyanate charge transport coating composition, which can then be blended with a hydroxyl pendant polycarbonate. The resulting coating composition can then be deposited on a photogenerating layer of a photoconductive imaging member and/or the coating composition can be deposited on a charge transport layer, followed by curing in each instance.
Moreover, in embodiments of the present invention there is provided a charge transport (CT) composition comprised of charge transport molecules or compounds of, for example, aryl amines, a hydroxylated charge transport compound (CTM) or mixtures thereof, a hydroxyl pendant polycarbonate binder, and a curing agent which reacts with the CTM hydroxy group and polymer binder to form a prepolymer solution on reaction with a suitably functionalized difunctional compound such as a diisocyanate. The resulting composition can be applied or deposited as a charge transport layer in a photoconductive imaging member containing a photogenerating layer, and other known appropriate layers. On thermal curing at elevated temperatures a crosslinked polymeric network having excellent stability in all three dimensional directions is formed. The resulting crosslinked composition, such as, for example, crosslinked at from about 5 percent to about 75 percent, permits wear resistant and extended lifetimes for the photoconductive imaging member. Therefore, the charge transport layer may contain suitable percentages of charge, such as hole transport molecules, with the remainder being the crosslinked compositions illustrated herein, and wherein each of the free charge transport compounds and the functionalized CTM contribute to charge transport. Thus, the amount of free charge transport compounds selected can be reduced without or with only minimum adverse impacts on the electrical performance of the photoconductive imaging members.
Moreover, in embodiments thereof the present invention imaging members can contain a hole blocking, or undercoat layer (UCL) comprised of, for example, siloxane, such as tetraethoxysilane (TEOS) and 3-aminopropyl trimethoxysilane (γ-APS), a metal oxide, such as titanium oxide, dispersed in a phenolic resin/phenolic resin blend or a phenolic resin/phenolic compound blend, and further wherein this layer is modified by incorporating therein an in situ formed organic/inorganic network, and which network can, for example, enable thicker hole blocking layers and permit excellent, and in embodiments improved electron transporting characteristics by, for example, providing additional electron transporting paths, and which layer can be deposited on a supporting substrate. More specifically, the hole blocking layer usually in contact with the supporting substrate can be situated between the supporting substrate and the photogenerating layer, which is comprised, for example, of the photogenerating pigments of U.S. Pat. No. 5,482,811, the disclosure of which is totally incorporated herein by reference, especially Type V hydroxygallium phthalocyanine, and generally metal free phthalocyanines, metal phthalocyanines, perylenes, titanyl phthalocyanines, hydroxy gallium phthalocyanines, selenium, selenium alloys, and the like.
The imaging members of the present invention in embodiments exhibit excellent cyclic/environmental stability, and substantially no adverse changes in their performance over extended time periods; resistance to wear and excellent imaging member lifetimes exceeding, for example, 1,000,000 imaging cycles; excellent and improved electrical characteristics; low and excellent Vlow, that is the surface potential of the imaging member subsequent to a certain light exposure, and which Vlow is, for example, about 20 to about 100 volts lower than, for example, related imaging members free of the crosslinkable polycarbonate illustrated herein.
The photoresponsive, or photoconductive imaging members can be negatively charged when the photogenerating layers are situated between the hole transport layer and the hole blocking layer deposited on the substrate.
Processes of imaging, especially xerographic imaging and printing, including digital, are also encompassed by the present invention. More specifically, the layered photoconductive imaging members of the present invention can be selected for a number of different known imaging and printing processes including, for example, electrophotographic imaging processes, especially xerographic imaging and printing processes wherein charged latent images are rendered visible with toner compositions of an appropriate charge polarity. The imaging members are in embodiments sensitive in the wavelength region of, for example, from about 500 to about 900 nanometers, and in particular from about 650 to about 850 nanometers, thus diode lasers can be selected as the light source. Moreover, the imaging members of this invention are useful in color xerographic applications, particularly high-speed color copying and printing processes.